1. Field of the Invention
The present invention relates to a converter system converting power. More particularly, the present invention relates to a converter system technology for operating a plurality of converter modules in parallel with optimum efficiency.
2. Description of the Prior Art
Unlike solar or wind power, fuel cells are representative renewable distributed energy sources of which an output can be controlled according to a user demand characteristic and are widely used as power supply sources of a mobile system such as an unmanned aerial vehicle, an automobile, a submarine and the like at present. Miniaturization and high power of fuel cell stacks applied to the mobile system are very important factors to reduce the weight of the system and improve the efficiency of the system.
Meanwhile, a DC-DC converter is used for efficient power conversion of the high power fuel cell stack. When modules having the same capacity are arranged in parallel in an interleaving type, the DC-DC converter may relatively easily increase processing power and reduce current ripple.
However, such a parallel arrangement type corresponds to a very advantageous structure to the reliability improvement and the increase in processing power, but has disadvantages in that power is easily non-uniformly processed between parallel modules and a high efficiency operation is difficult during entire load operation intervals. Particularly, the mobile system requires as long an operation as possible with limited fuel, and accordingly, loss reduction through the high efficiency of the DC-DC converter is a very important factor.